_As millions of Americans sit down to celebrate Thanksgiving today, some Native Americans are pushing back, urging the country to remember the implications of white settlement on indigenous cultures.As they have for decades, hundreds of people participated in a “National Day of Mourning” in Plymouth, Mass.

on Thursday afternoon near where the first Thanksgiving is thought to have taken place. Not everyone wants to hear that message while gorging on turkey and filling Facebook with thanks for friends, families and good lives.

“Sometimes we’re told to go back where we came from, which is pretty ironic,” said Mahtowin Munro, co-leader of United American Indians of New England, which organizes the annual protest march.

Some of the frustration centers around what some Native Americans see as their relegation to supporting players at that first celebration, rather than people with long-existing culture, knowledge and government. History puts the first thanksgiving in 1621 at Plymouth, between Pilgrims and members of the Wampanoag tribe.

"They are depicted as nameless, faceless, generic “Indians” who merely shared a meal with the intrepid Pilgrims. The real story is much deeper, richer, and more nuanced,” says the National Museum of the American Indian, which this year released a guide for teachers covering Thanksgiving. "For the English, interaction with the Wampanoags enabled their colony’s survival. Although the English were interlopers, the Wampanoags shared their land, food, and knowledge of the environment.”

The museum suggests that teachers help students understand that Native Americans haven’t vanished from American life, even through many were forcibly resettled from their traditional lands onto reservations in far less desirable areas, to make room for European-style farming and villages.

Munro said her objection to Thanksgiving is the cultural whitewashing that allows most Americans to ignore what happened to the native population. She said most people are taught a “fantasy history” that ignores or downplays the widespread slaughter of her people and the theft of their traditional lands, the damming of their rivers, and the deliberate slaughter of bison. For them, the Thanksgiving holiday remains an affront.

“As indigenous people, we’ve been taught by our elders to give thanks every day,” she said. "We are a people who have survived genocide. People able to gather with our families is very important to us.”